Browsing by Author "Chen, Kai-Wei"

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Effects of initial GaN growth mode on the material and electrical properties of AlGaN/GaN high-electron-mobility transistors
(2014-09-01)
Wong, Yuen-Yee
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Chang, Edward Yi
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Huang, Wei-Ching
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Lin, Yueh-Chin
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Tu, Yung-Yi
AlGaN/GaN high-electron-mobility transistors (HEMTs) with different initial GaN growth modes were prepared on AIN/sapphire substrates. Secondary ion mass spectroscopy and Hall effect measurements confirmed that a highly conductive n-type region was generated at the GaN/AIN buffer interface during the three-dimensional to two-dimensional (3D-2D) growth mode transition. This n-type region was created by oxygen impurity incorporation during the 3D-2D growth mode transition, and its thickness increased with the transition time. The existence of this n-type conduction path not only changed the material properties but also degraded the device performance of HEMTs. (C) 2014 The Japan Society of Applied Physics
Investigation of the low-temperature AlGaN interlayer in AlGaN/GaN/AlGaN double heterostructure on Si substrate
(2014-11-01)
Hsiao, Yu-Lin
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Wang, Yi-Jie
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Chang, Chia-Ao
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Weng, You-Chen
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Chen, Yen-Yu
A low-temperature (LT) AlGaN interlayer is inserted in the Al0.1Ga0.9N back barrier layer of an Al0.2Ga0.8N/GaN/Al0.1Ga0.9N double heterostructure grown on a 150mm Si substrate. It is found that the 21-nm-thick LT-AlGaN interlayer plays an important role in stress relaxation and dislocation reduction of the Al0.1Ga0.9N back barrier layer, especially for screw dislocation reduction. In addition, a buffer breakdown voltage higher than 600V is achieved, which is much higher than those of conventional heterostructures. These results demonstrate the effectiveness of combining the LT-AlGaN interlayer and the Al0.2Ga0.8N/GaN/Al0.1Ga0.9N double heterostructure on a Si substrate to increase the breakdown voltage for high-power applications. (C) 2014 The Japan Society of Applied Physics
Investigations of GaN growth on the sapphire substrate by MOCVD method with different AlN buffer deposition temperatures
(2016-04)
Huang, Wei-Ching
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Chu, Chung-Ming
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Wong, Yuen Yee
;
Chen, Kai-Wei
;
Lin, Yen-Ku
The effects of different AlN buffer deposition temperatures on the GaN material properties grown on sapphire substrate was investigated. At relatively higher AlN buffer growth temperature, the surface morphology of subsequent grown GaN layer was decorated with island-like structure and revealed the mixed-polarity characteristics. In addition, the density of screw TD and leakage current in the GaN film was also increased. The occurrence of mixed-polarity GaN material result could be from unintentional nitridation of the sapphire substrate by ammonia (NH3) precursor at the beginning of the AlN buffer layer growth. By using two-step temperature growth process for the buffer layer, the unintentional nitridation could be effectively suppressed. The GaN film grown on this buffer layer exhibited a smooth surface, single polarity, high crystalline quality and high resistivity. AlGaN/GaN high electron-mobility transistor (HEMT) devices were also successfully fabricated by using the two-step AlN buffer layer. (C) 2016 Elsevier Ltd. All rights reserved.
The Effect of the Thickness of the Low Temperature AlN Nucleation Layer on the Material Properties of GaN Grown on a Double-Step AlN Buffer Layer by the MOCVD Method
(2016-02)
Huang, Wei-Ching
;
Chu, Chung-Ming
;
Hsieh, Chi-Feng
;
Wong, Yuen-Yee
;
Chen, Kai-Wei
The influence of low-temperature AlN (LT-AlN) nucleation layer thickness on the material properties of the GaN layer grown on the double-step AlN layer is investigated. When GaN was grown without the LT-AlN nucleation layer, the GaN layer has low sheet resistance of 464 ohm/sq and the surface was decorated with pitted region. On the other hand, when a LT-AlN layer with a thickness of 5 nm was inserted, a GaN layer with sheet resistance higher than 10(6) ohm/sq was achieved. This thin nucleation layer also improved the GaN morphology, suppressed inversion domain formation, and reduced oxygen impurity incorporation. However, the surface morphology and quality of the GaN crystal were severely degraded when the LT-AlN thickness was increased to 10 nm due to the formation of disorientated grains in the LT-AlN layer.